👀 Views: 31 💬 Answers: 1 📅 Created: 2025-07-31

sql-server cte recursive-query hierarchical-data SQL

I've hit a wall trying to I tried several approaches but none seem to work... I'm trying to configure I've searched everywhere and can't find a clear answer. I'm encountering unexpected results when using a Common Table Expression (CTE) for recursive queries on hierarchical data in SQL Server 2019. The requirement is to retrieve all ancestors of a specific node in a parent-child relationship table, but the results are inconsistent. I've defined my CTE as follows: ```sql WITH RecursiveCTE AS ( SELECT Id, ParentId, Name FROM Hierarchy WHERE Id = @NodeId -- the specific node ID we start with UNION ALL SELECT h.Id, h.ParentId, h.Name FROM Hierarchy h INNER JOIN RecursiveCTE r ON h.Id = r.ParentId ) SELECT * FROM RecursiveCTE; ``` However, when I execute this query, I sometimes get duplicate rows for the same ancestor, which shouldn't happen. I've tried adding a `DISTINCT` clause to the final `SELECT`, but that feels like a workaround rather than a solution. Additionally, I verified that the data in the `Hierarchy` table is correct and does not contain duplicates. Here's a sample of the data in the `Hierarchy` table: | Id | ParentId | Name | |----|----------|------------| | 1 | NULL | Root | | 2 | 1 | Child 1 | | 3 | 1 | Child 2 | | 4 | 2 | Grandchild 1| | 5 | 2 | Grandchild 2| In some cases, when I run the query for `@NodeId = 4`, I receive multiple entries for 'Child 1'. This behavior seems to depend on the data structure I have, and I suspect it might be related to how the recursive join is structured. Is there something I'm overlooking in the CTE definition, or a best practice for ensuring unique results in such queries? Any help would be greatly appreciated! For context: I'm using Sql on Ubuntu. Any help would be greatly appreciated! I'm working on a web app that needs to handle this. Any help would be greatly appreciated! The stack includes Sql and several other technologies. Am I approaching this the right way? My team is using Sql for this desktop app. What would be the recommended way to handle this? I'm using Sql latest in this project. Is there a better approach? Any advice would be much appreciated. I'm working on a application that needs to handle this. I appreciate any insights!